MASON, Texas - On a YouTube clip that has gone viral, brash Texas handgun instructor Crockett Keller defiantly tells Muslims and non-Christian Arabs he won't teach them how to handle a firearm.

State officials see the ad as possible discrimination, and may revoke Keller's instructor license.

Tens of thousands of YouTube viewers have watched the $175 ad for Keller's business in the small community of Mason, which has won him a handful of admirers but that embarrassed locals say misrepresents their community. Muslim groups dismissed the 65-year-old a bigot.

Among the couple of thousand residents in the Central Texas town, Keller has other reputations.

"He's a character and likes attention," said Diane Eames, a jeweler with a downtown shop in Mason's quaint town square.

Keller has received plenty of attention since his radio spot on a rural country music station in Mason County, east of Austin, went viral on the Internet. Keller said he whipped up the script on his iPad in 10 minutes. The ad quit airing last week.

"If you are a socialist liberal and/or voted for the current campaigner-in-chief, please do not take this class," Keller says in the ad's closing seconds, also taking a swipe at President Barack Obama. "You've already proven that you cannot make a knowledgeable and prudent decision as required under the law. Also, if you are a non-Christian Arab or Muslim, I will not teach you this class. Once again, with no shame, I am Crockett Keller."

The Texas Council on American-Islamic Relations called the ad ugly rhetoric undeserving of media attention. Others have called Keller's phone number from the ad to personally tell him worse, including alleged death threats.

The Texas Department of Public Safety is now investigating whether to revoke or suspend Keller's license to teach concealed handgun courses.

"Conduct by an instructor that denied service to individuals on the basis of race, ethnicity or religion would place that instructor's certification by the Department at risk of suspension or revocation," the department said in a statement.

Inside a remote highway cabin on the edge of the Llano River, where a draped, full-size canon is parked across from his desk, Keller said the ad was inspired after being "flabbergasted" by a couple neighbours who left the state to campaign for Obama. As for refusing to teach Muslims, Keller described that as an afterthought tacked onto the spot, which he couldn't remember but said was likely generated from something in the news.

"I got to thinking, 'Hmm, I'm arming the enemy,'" Keller said.

Of course, even Keller knows that Muslims were unlikely to show up at his door asking to take his $100 course.

Mason County, as Eames described it, is "white bread" — the population was 93 per cent Caucasian in the latest Census, and all Republican statewide candidates won with at least 70 per cent of the vote in 2010. Keller said he wasn't aware of any Muslims in Mason County, nor could a handful of locals name one.

Eames and Joyce Arnold, a real estate agent, said they worried about the radio spot embarrassing the city. Eames ran what she described as a successful sex-toy business in Mason before opening the jewelry store, and Scott Haupert, co-owner of the Sandstone Cellars Winery, said Mason is more tolerant than Keller's comments would suggest.

"I voted for Obama and I'll vote for Obama again," said Haupert, an avowed Democrat.

But Keller has also won over some fans. As he spoke with a reporter in his cabin, rancher Clyde McCarley knocked on his door and asked about signing up for a class.

"It's mighty dadgum interesting to me that some people can say anything they want, and you make a statement and they bring down the house on you," McCarley said.

Mustafaa Carroll, executive director of the Texas Council on American-Islamic Relations, said the group is watching how the state responds to Keller's ad and whether the agency revokes his instructor license.

"We try not to give too much credibility to some of these people who do outlandish things," Carroll said. "But there are some issues that we do have to address."